Typical microwave components and subsystems comprise metal, or at least metal-coated, enclosures that form cavities for mounting monolithic microwave integrated circuits (MMIC) chips and other components, which can include amplifiers. These enclosures include lids that physically protect the MMIC chips, wire-bonds, and other components from damage in manufacture and use and from the external environment. The lids also protect the components from interference caused by electromagnetic radiation from the electronics in the rest of the system and the operating environment.
Microwave circuits typically radiate energy, such as from interconnect tracks, bond wires, and/or the chips themselves. At certain frequencies, the energy can dominate the functionality and destroy performance of the chips. For example, radiated energy can couple into other parts of the circuit and can often cause unwanted or catastrophic behavior, such as resonance in the “cavity” that houses the MMIC chips. Resonances often cause amplifiers to oscillate, which can render a microwave module completely non-functional. The ease with which unwanted radiation “leaks” into and affects all parts of a system presents a substantial challenge. A typical approach to managing these problems is to package microwave chips with radiation-absorbent material, such as a thin sheet of radiation-absorbent material attached to an underside of a module's lid, or metal or dielectric posts located inside a module to suppress cavity resonances and stray radiation coupling.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.